Jinx wrote:
>
> > Where you can win is if you can get a phase change somewhere
> > in your temperature range. You can store 10 or 20 times more
> > energy in a solid-liquid or liquid-gas phase change than in the
> > whole temperature swing between  0 & 100 degrees C.
>
> At the link I provided they are using solid Sodium Sulphate. This
> melts during the day and releases its heat at night
>
> The story with the greenhouse heater was that you'd use the fully
> hydrated Sodium Sulphate (Na2SO4.10H20 - not an uncommon
> salt), not the anhydrous form. This has obviously been looked into
> by whover it was I got the suggestion from, and shown to give
> better results.
>
> For such a small box, I think some chemical heat storage is
> worth a crack. If the circuit is also giving off some heat that
> will help
>
> What's the possibility of using a one-way mirror to collect
> heat through that will act as a (mediocre) insulator by internal
> reflection at night, like a Thermos flask ?


Maybe aluminium foil, a few hand packed layers
would only be a few mm thick but have trapped
air layers. I don't know how good it would be,
but it's easy to try, at least, just stick the
3W resistor in the box put the box in the freezer.
:o)
-Roman

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